Tingting Hou,Nengchao Luo,Hongji Li,Marc Heggen,Jianmin Lu,Yehong Wang,Feng Wang
Selective cleavage of C–C bonds is pursued as a useful chemical transformation method in biomass utilization. Herein, we report a hybrid CuOx/ceria/anatase nanotube catalyst in the selective oxidation of C–C bonds under visible light irradiation. Using the lignin β-1 model as a substrate offers 96% yields of benzaldehydes. Characterization results by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectroscopy element (EDX) mapping reveal that CuOx clusters are highly dispersed on the exposed anatase surface as well as on the nanosized ceria domains. In-depth investigations by Raman and ultraviolet visible diffuse reflectance spectra (UV−vis DRS), together with density functional theory (DFT) calculations, further verify that the CuOx clusters present on the ceria domains increase the concentration of surface defects (Ce3+ ions and oxygen vacancies) and accordingly improve the photocatalytic activity (Yang character); the CuOx clusters decorating on anatase suppress the side reaction (oxy-dehydrogenation without C–C bond cleavage) because of an upward shift in the valence band (VB) edge of anatase (Yin character). Mechanism investigation indicates hydrogen abstraction from β-carbon by photogenerated holes is a vital step in the conversion.
Rui Zhu,Gongyu Zhou,Jia-nan Teng,Xinglong Li,Yao Fu
Graphical Oxidative cleavage : A heterogeneous metal-free photocatalytic system is developed for oxidative cleavage of C−C bonds in 1,2-diols at mild conditions (visible light, room temperature, no base, O 2 balloon). The reaction mechanism is studied through a series of control experiments and DFT calculations. In addition, the catalytic system has a broad substrate scope, including aliphatic, benzylic, alkenyl 1,2-diols, and α-hydroxy acids such as lactic acid. The preparation of carbonyl compounds by the aerobic oxidative cleavage of C−C bonds in 1,2-diols under mild reaction conditions is a very significant reaction and is widely employed in various scenarios. Avoiding the use of harmful stoichiometric oxidants and adopting a greener chemical process remain a challenge for this reaction to date. In this manuscript, a heterogeneous metal-free photocatalytic strategy without any additive was developed for aerobic oxidative cleavage of C−C bonds in 1,2-diols at ambient conditions with visible light. The reaction mechanism was further studied through a series of control experiments and density functional theory (DFT) calculations. In addition, the catalytic system showed a broad substrates scope, including aliphatic (linear or cyclic) 1,2-diols, benzylic, alkenyl 1,2-diols, and α-hydroxy acids (such as lactic acid). Thus, this strategy could serve as a method for the transformation of 1,2-diols to corresponding carbonyl compounds by the aerobic oxidative cleavage of C−C bonds.
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